Vehicle wheel having a large contact surface area

ABSTRACT

A vehicle having a rim and a wheel disk center or convex wheel disk which is connected thereto and is secured by a hub or brake drum with a plurality of connection bosses for the wheel bolt holes arranged along the circumference of the bolt pitch circle. The connection bosses have a spherical or conical countersink, and the region surrounding the countersink is cambered outward. The wheel disk center or convex wheel disk has contact surfaces for the hub or brake drum which are distributed along the circumference. The region of the connection boss which surrounds the countersink, is significantly thicker in all cross-sectional planes than the more remote region which forms the wheel disk center or convex wheel disk. The region surrounding the countersink forms an integral unit with the more remote region. The region directly adjoining the countersink has the greatest thickness which continuously decreases radially outward as viewed from the axis of the countersink, and then merges in a rounded or tangential manner into the region which has a virtually constant thickness which corresponds substantially to the initial thickness of the round blank for the integral forming of the wheel disk center or convex wheel disk.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention is directed to a vehicle wheel.

2. Discussion of the Prior Art

When a vehicle wheel, comprising a rim and a wheel disk center andconvex wheel disk which are connected therewith, is mounted on avehicle, the wheel disk center or convex wheel disk is connected in africtional engagement with the hub or brake drum by wheel bolts. Thewheel bolts are tightened by a torque wrench in order to generate adefined, sufficiently large longitudinal force along the bolt. Themagnitude of the required bolt longitudinal force is determined, amongothers factors, by the quantity of bolts, the friction diameter of thecontact surfaces, the friction coefficients between the connectionelements, and the driving torque or braking torque to be transmitted. Anadded safety factor is imposed on the required bolt longitudinal forcewhich takes into account the forces acting on the bolt when the wheelsare rolling.

The connection boss and countersink of the wheel are clamped with thehub or brake drum via the longitudinal force of the bolt. Thecountersink has the function of opposing an elastic resilience to thebolt longitudinal force to the extent of elevated values such as occuras a result of misuse, e.g., oiled bolts or excessive tighteningtorques, since a plastic flow would lead to a decrease in the boltlongitudinal force and accordingly ultimately to a loosening of thewheel bolts.

Known constructions of connection bosses derive their spring rigidity inthe direction of the longitudinal axis of the bolt from a bending of thematerial arranged annularly around the countersink. Constructionalstiffening is known for the purpose of increasing spring rigidity overthat of normal plate thickness. One possibility consists in an inwardreverse drawing or camber of the region of the connection boss locatedinside radially. Moreover, this shape has the advantage of an outwardenlargement of the contact surface relative to the wheel bolts comparedwith a simple camber. For example, reference is had to the wheel catalogof Mannesmann Kronprinz AG, 1990/1991 Issue, bottom of page 28. Adisadvantage in prior constructions of the connection boss is the cleardependency of the stiffness of the connection boss on the platethickness and on the material strength of the starting material.

A wheel comprising a profiled rim and a convex wheel disk connectedtherewith in the drop base region by means of welding is known from U.S.Pat. No. 3,664,708. To prevent cracking in the connection boss as theresult of excessive tightening of the wheel bolts, it is suggested toarrange a flange-like bushing in the connection boss. The region of thebushing constructed in the manner of a flange lies on the side facingthe hub or brake drum and must be inserted through the connection bossbefore the wheel is mounted. After placement on the wheel, a cone of thefront region of the bushing is formed by of tightening the wheel nut.This cone comes to rest on the edge region of the connection boss, butonly when the end face of the flange-like region of the bushing rests onthe hub or brake drum. A disadvantage in this design is that specialbushings must be produced which can easily fall out of the connectionboss during the mounting of the wheel until the cone fixing the bushingis formed. Further, this arrangement is suitable only for wheels withstud pins arranged at the hub or brake drum, since the bushings can fallout easily during mounting in the otherwise conventional wheel boltfastening. Another disadvantage consists in that the bushing always fitsonly one type of wheel, so that for a hundred different wheel types, ahundred different bushings will have to be produced and stocked.Further, confusion can lead to the wrong bushing being used. Anotherdisadvantage is that at least two setting gaps remain as a result of thetwo-part arrangement. This is very prejudicial to the stability of thebolt longitudinal force. Moreover, the bending spring is already highlyloaded in the course of mounting, since the cone of the bushing isformed by means of the wheel nut.

French reference FR-A-25 39 079 discloses a special wheel hubconstruction. The sole figure shows a section of the vehicle wheel,including a region of the convex wheel disk. The convex wheel disk isprovided with a plurality of connection bosses for the wheel bolt holesarranged along the circumference of the bolt pitch circle. Theconnection boss has a conical countersink, and the region surroundingthe countersink is cambered outward. The region of the connection bosssurrounding the countersink is significantly thicker and allcross-sectional planes than the more remote region of the convex wheeldisk. The region directly adjoining the countersink has the greatestthickness which then decreases in a continuous manner radially outwardas viewed from the axis of the countersink and then merges in a roundedmanner into the adjoining region. This adjoining region has a virtuallyconstant thickness which corresponds substantially to the initialthickness of the round blank for the integral forming of the convexwheel disk.

SUMMARY OF THE INVENTION

It is the object of the invention to provide a vehicle wheel comprisinga rim and a wheel disk center or convex wheel disk connected therewith,preferably a metal wheel disk center or convex wheel disk, in particularmanufactured from light metal, which is simple to mount and reliablyprevents a loosening of the wheel bolts during driving. Further, a largecontact surface is provided for preventing area pressure at the wheelbolts.

According to the invention, the region surrounding the countersink issignificantly thicker than a process-related conventional tapering. Theregion directly adjoining the countersink has the greatest thicknesswhich decreases continuously radially outward and merges in a roundedmanner or tangentially in the adjoining region. This adjoining region ischaracterized in that it has a virtually constant thickness whichsubstantially corresponds to the initial thickness of the round blankfor producing the wheel disk center or convex wheel disk. The stiffnessof the connection boss acting as a bending a spring is increased by thedeliberate upsetting in the countersink region. Further, there isincreased resistance against an expansion of the countersink whentightening the wheel bolt. The thickness of the rest of the plate canaccordingly be reduced to a minimum, since the weak point--theconnection boss--has a sufficient stiffness which also makes allowancefor incorrect use of the wheel bolts. The increase in thickness ispreferably effected axially outward in order to form the largestpossible contact surface between the wheel bolt and the countersink. Inso doing, however, the limitation consisting of the prescribedconnection dimensions must be taken into account. In every case, thesurface pressure between the wheel bolt and the countersink is minimizedby the increased contact surface. The suggested formation of theconnection boss is applicable for all wheels made from metal, butparticularly those made from light metal, since this material, by itsnature, brings about a reduction in strength. In order to make the weakpoint--the connection boss--more reliable for wheels of light metal, itis suggested in a further embodiment to press material inward axially,in addition, so as to form a toroidal ring. The spring stiffness of theconnection boss is substantially increased in this way, since thestiffness of the toroidal ring acting as a pressure spring is added tothe bending component of the surrounding region. The ring is supportedon the hub or brake drum while the wheel bolt is being tightened. Whennot screwed on, the end face of the toroidal ring has a defined gapheight relative to the contact surface on the hub or brake drum. Thisspacing is used for adapting the interaction between the bending springand pressure spring and accordingly for influencing the boltlongitudinal force of the tightening torque.

This toroidal ring has the advantage that a plastic deformation of theregion subjected to bending load is prevented and a spring stiffness canbe adjusted over the geometric formation of the ring so as to beextensively independent from the utilized material with respect tostrength and thickness. It has proven advantageous when the toroidalring is enclosed by an annular groove or a rounded recess. The lattervariant is particularly advantageous for steel wheels, since the risk ofcracking in the region of transition from the groove to the ring isaccordingly reduced.

The suggested construction is particularly advantageous for a lightmetal wheel manufactured from plate metal, but is equally suitable for asteel wheel or a cast light metal wheel. The countersink constructionaccording to the invention has the substantial advantage that it meetsthe automobile industry demand for wheel bolts which are as homogeneousas possible, since the countersink stiffness can be adapted extensivelyindependently from the height of the countersink and the initialthickness of the starting material.

In the production of the vehicle wheel according to the invention, incontrast to the known prior art, in the forming of the connection bossthe material volume to be punched out or stamped out is reduced and thematerial economized in this way is displaced by upsetting from thesubsequent countersink into the adjoining region by means of anoptimized pressing and cambering with simultaneous variable holding. Inaddition, in the formation of the toroidal ring, especially in theproduction of light metal wheels, material is pressed axially inward bymeans of axial pressing.

The vehicle wheel according to the invention is explained more fully inthe drawing with reference to several embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view in partial section of a firstembodiment of the vehicle wheel according to the invention in the regionof the connection boss;

FIG. 2 shows a second embodiment through the same cross section as inFIG. 1;

FIG. 3 shows a third embodiment through the same cross section as inFIG. 2;

FIG. 4 shows the embodiment in FIG. 2 in combination with a wheel boltand the hub or brake drum in a state of use;

FIG. 5a and is a top view of the outside of the convex wheel disk;

FIG. 5b shows a section A--A in FIG. 5a and;

FIG. 5c shows a section B--B in FIG. 5b.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a cross-sectional view of a partial section of a firstembodiment of the vehicle wheel according to the invention in the regionof the connection boss 1. The connection boss 1 has a conically formedcountersink 2 with a cone angle of 60°, for example. The connection boss1 is cambered outward beyond the adjoining region 3, 4 in a knownmanner. Part of the adjoining portion of the convex wheel disk 5 isindicated here. According to the invention, the region 6 surrounding thecountersink is significantly thicker than the region forming the convexwheel disk 5. The region directly adjoining the countersink 2 has thegreatest thickness which then continuously decreases outward radiallyconsidered from the axis 7 of the countersink 2 and then merges in arounded manner or tangentially, as the case may be, in the adjoiningregion 3, 4. The dashed lines and solid lines somewhat below theconnection boss 1 show, by way of example, the region 8 of the wheeldisk center and convex wheel disk 8 lying between two connection bosses1 as seen in the circumferential direction. The thickness 9 in theimmediate area of the countersink 2 is at least 15%, preferably morethan 25%, greater in comparison with the thickness 10 of the regionforming the convex wheel disk 5. In addition to the increase instiffness of the connection boss 1, the upset material, according to theinvention, in the countersink region brings about an enlargement of thecontact surface 11 with the wheel bolt 24 (see also FIG. 4). For thisreason, the thickness increase is preferably directed outward axially,wherein, however, the prescribed connection dimensions indicated byarrow 12 should be taken into account.

FIG. 2 is a cross-sectional view identical to that shown in FIG. 1showing a second embodiment, wherein the same reference numbers havebeen selected for identical parts. In contrast to FIG. 1, the connectionboss 1' has an inwardly directed toroidal ring 13' which is definedradially inside by the cylindrical part 14' of the bolt hole 15 whoseextension, according to the invention, can be greater than the materialthickness 16', 17' of the adjoining regions 3', 4' in the axialdirection. The end face 18 of the toroidal ring 13' has a defined gapheight 20 relative to the contact surface 19 of the wheel locatedoutside radially when not in the screwed on state. The point ofapplication of the ring 13' acting as pressure spring can be adaptedrelative to the surrounding region 3', 4' acting as bending spring. Thespring rigidity of the toroidal ring 13' is substantially determined bythe material volume utilized as a spring which can be determined, forexample, by the breadth and depth of the annular groove 21. Duringmounting and subsequent tightening of the wheel bolt 24 (see FIG. 4),the contact surface 19 arranged radially outside first contacts thecontact surface 26 of the hub 25. When the tightening torque of thewheel bolt 24 is increased to the value generally established by thevehicle manufacturer, the contact surface 22' located on the radialinside of the wheel now contacts the contact surface 26 of the hub 25(see FIG. 4). From this point, the surrounding region 3', 4' of theconnection boss 1' acts as a bending spring until the end face 18 comesinto contact with the contact surface of the hub 25 and the toroidalring 13' acts additionally as a pressure spring. The embodiment shown inFIG. 2 is preferably applied for light metal wheels to compensate forthe reduced strength of material at the weak point represented by theconnection boss 1'.

FIG. 3 shows a cross-sectional view identical to that shown in FIG. 2showing a third embodiment of the region according to the invention.Again, the same reference numbers are used for identical parts with theaddition of a prime. In contrast to FIG. 2, the countersink 23 isspherical. The fundamental arrangement and manner of operation of theconstruction of the connection boss 1' according to the invention arethe same as described above. However, the transition from the toroidalring 13' to the adjacent regions 3', 4' are configured somewhatdifferently. Instead of a stamped annular groove 21 (FIG. 2), a more orless rounded recess 27 is provided in the present embodiment. Thisembodiment is preferably used in steel wheels.

FIG. 4 is identical to the embodiment shown in FIG. 2; however, FIG. 4shows the cooperation of the connection boss, according to theinvention, of the wheel disk center or convex wheel disk 5' with a wheelbolt 24 and a part of the hub or brake drum 25. The drawing shows thestate at the moment when the radially outwardly arranged contact surface19 of the wheel is in contact with the contact surface 26 of the hub 25,but no bolt longitudinal force is as yet in effect. The stepped contactof the individual surface regions with the contact surface 26 of the hub25 is only brought about by the actual tightening of the wheel bolt 24with a wrench or torque wrench.

FIGS. 5a to 5c show a top view and two sectional views of the vehiclewheel according to the invention. FIG. 5a shows the outside of theconvex wheel disk 5'. The embodiment of the connection bosses 1'substantially corresponds to the view shown in FIG. 3. FIG. 5a clearlyshows the stamped contact surfaces 30, 31. According to the invention,the contact surfaces 31 located outside radially are brought as close aspossible to the respective connection boss 1'. The wheel bolt 24 isrelieved of loading by this stamping. Since the distance between thewheel bolt 24 and effective contact surface 31 is small and the bendinglever arm is accordingly shortened, the wheel bolt 24 is relieved ofloading to the desired extent.

We claim:
 1. A vehicle wheel, comprising:a rim; one of a wheel diskcenter and a convex wheel disk each defining a plane and being connectedto the rim and having contact surfaces configured to be engagable withone of a hub and a brake drum; a plurality of connection bosses forwheel bolt holes, arranged on a circumference of a bolt pitch circle,each of the connection bosses having one of a spherical and a conicalcountersink, and a region that surrounds the countersink, is camberedaxially outwardly and is thicker in all cross-sectional planes than theone of the wheel disk center and the convex wheel disk, the regionsurrounding the countersink being formed as an integral part with theone of the wheel disk center and the convex wheel disk and beingconfigured to have a maximum thickness that decreases continuouslyradially outward from a center axis of the countersink and merges in aregion of the one of the wheel disk center and the convex wheel diskthat has a substantially constant thickness; and an inwardly directedtoroidal ring provided at each of the bosses so as to form an inwardlydirected increase in thickness, the toroidal ring being configured to becontactable with the one of the hub and the brake drum so as to form apressure spring with adaptable spring stiffness which acts in additionto spring stiffness from bending of a region adjoining the toroidalring, the toroidal ring being configured to form a defined gap relativeto the one of the hub and brake drum in a rest state, so that a point ofapplication of the pressure spring relative to the bending spring can bedetermined by dimensions of the gap, the one of the wheel disk centerand the convex wheel disk having contact surfaces arranged so as to bedistributed along the circumference on a radially outward side and on aradially inward side.
 2. A vehicle wheel according to claim 1, whereinthe spring stiffness of the toroidal ring acting as a pressure springcan be adapted by a quantity and configuration of a material volumeutilized for providing spring properties, so as to be extensivelyindependent from a thickness and strength of the material.
 3. A vehiclewheel according to claim 1, wherein an annular groove is arranged aroundthe toroidal ring.
 4. A vehicle wheel according to claim 1, wherein arounded recess configured to extend outwardly in a fiat manner isarranged around the toroidal ring.
 5. A vehicle wheel according to claim1, wherein each bolt hole has a cylindrical portion with a length in theaxial direction that is greater than a material thickness of the regionsadjoining the toroidal ring.